Environmental Considerations with Pine Straw Harvesting
Some forest managers are concerned that removing such quantities of pine straw may be detrimental to the productivity of the crop trees. Studies indicate that as few as two harvests within three years can reduce wood production of some stands by 50 cubic feet per acre compared to site with no pine straw harvesting performed.
Straw contains important nutrients like nitrogen, phosphorus, calcium, and magnesium that return to the soil as the straw breaks down. Raking straw removes these nutrients from forest stands. As the nutrients are removed, tree growth and vigor may decline. As much as 40 lbs of Nitrogen is lost for every 100 bales of straw per acre harvested. Poor nutrition will increase rotation length of the crop trees, decrease vigor, and make trees more susceptible to insect and disease. Fertilizer regimes may be essential to replenish the nutrients lost to pine straw harvesting and maintain or even improve the growth rate of the crop trees.
Since forest stands respond differently to fertilization, it is best to determine the required rates of nitrogen, phosphorus, and potassium, by performing a correct and thorough soil and foliar analysis. The County Extension Agent or local Texas Forest Service forester can provide assistance.
Typical fertilization recommendations, however, generally suggest broadcasting 150 to 200 lbs of nitrogen per acre and 50 lbs of elemental phosphorus per acre every five years. Broadcast 250 lbs of DAP per acre will apply about 45 lbs of the nitrogen and the 50 lbs of phosphorus needed. The additional 100 to 150 lbs of nitrogen per acre can be applied as urea fertilizer. Trees use phosphorus to increase wood growth, and nitrogen stimulates foliage growth and thereby pine straw yields. Potassium might also be supplemented at a rate of 50 to 80 pounds per acre. Apply fertilizer in late January or early February. Typical application will cost between $25 and $55 per acre.
Soil and Water
As with the landscape bed, pine straw on the forest floor has many other benefits. One of which is the moisture holding capacity of partially decayed straw important for tree survival and growth during hot summer months and water stress periods. In fact, plant growth reduction is often attributed to water stress. Straw also helps to insulate the soil from temperature extremes that can also reduce tree growth.
Another concern is that the removal of pine straw exposes the soil causing erosion and loss of topsoil. To this end, it is important for harvesting operations to leave a thin layer of straw and organic matter.
Raking straw can impact the diversity and richness of plant and animal species. Harvesting pine straw from the site can dramatically alter the natural, ecological system because pine needles provide food and habitat for many animals that help decompose litter, improve soil tilth, and serve as food for wildlife. Furthermore, harvesting pine straw may have long-term affects on soil chemistry (e.g., from acidic to neutral or basic) that are not yet fully understood. For these reasons, it is desirable to identify unique and/or sensitive areas and shield them from straw production. Raking every 4 years may also reduce any long-term deleterious effects. A blade attached vertically to a tractor can be used to prune trees quickly.
Sensitive areas such as this stream side should be protected from regular pine straw removal.